Can trauma be transmitted intergenerationally?

Dr. Rachel Yehuda reveals groundbreaking research on trauma and its biological risk factors

Before post-traumatic stress disorder (PTSD) was officially identified in 1980, little was known about the repercussions of a traumatic incident. “In general, when we talk about the effects of trauma, we are talking about a moving target,” said Dr. Rachel Yehuda. “We are talking about a dynamic process that moves and develops and changes. We are not talking about something that is static.”

Yehuda’s focus on PTSD is part of her broader research in epigenetics—the study of changes in gene expression rather than alterations to the genetic code. “Some of the epigenetic changes are inheritable, but others can occur in development in response to environmental influences and particularly in uterine influences,” Yehuda explained to an audience at Dawson College on Oct. 16.

Yehuda is a professor of neuroscience and the vice-chair of psychiatry at the Icahn School of Medicine at Mount Sinai in New York City. She is also the mental healthcare patient director at the Veteran Affairs Medical Center in Bronx, N.Y. She has authored more than 250 published papers, chapters and books in the field of traumatic stress and the neurobiology of PTSD. Her epigenetics research led her to studying the children of Holocaust survivors and pregnant women who survived the 9/11 attacks. The purpose was to demonstrate how traumatic stress can be transmitted biologically to the next generation.

“I was studying the effects of stress and learning something that I thought was quite fascinating which was how stress hormones affect the brain and brain development in particular,” she said. Yehuda received her PhD in psychology and neurochemistry and her master of science in biological psychology from the University of Massachusetts Amherst, which allowed her to pursue the study of stress psychology further. While she was earning her PhD, PTSD was a relatively new diagnosis. “This was the first recognition by psychiatry that the effects of a traumatic stressor could be long-lasting,” she said. “It was a very brave thing to do because stress research didn’t really offer a paradigm for understanding this.”

In 1991, Yehuda became an assistant professor of psychiatry at the Icahn School of Medicine at Mount Sinai. “I became very fascinated with some questions after I became acquainted with the concept of PTSD,” she said. According to Yehuda, the main question on her mind was why the effects of trauma endure once a traumatic event is over. She also studied the factors that cause people to react differently to trauma “because, surely, we don’t all respond the same way,” she said. “Why do survivors feel transformed by traumatic experiences?”

According to Yehuda, when a person experiences fear, their fight-or-flight response is activated. “The startle response orients you to danger. All the things that your body might have been doing at the time of trauma—like ovulation or digesting your lunch—all these things had to slow down so that all your energy could be preserved […] to increase your heart rate, blood pressure and cause the release of adrenaline,” she said.

When the brain senses the immediate danger has passed, it sends a signal to the adrenal glands to release cortisol. This hormone has the effect of reducing the amount of adrenaline circulating in a person’s system. According to Yehuda, the more severe the stressor, the more cortisol is secreted to bring the body back to normal.

“It’s a really well-balanced system that is designed to activate and calm itself down,” she said.

What Yehuda discovered during a clinical study in 1991, however, was that Vietnam war veterans with PTSD had lower levels of cortisol in their systems at the time compared to Vietnam veterans who didn’t have the disorder. “I couldn’t understand what would explain why a trauma survivor would have low cortisol,” she said.

In an attempt to understand these results, Yehuda spoke with her postdoctoral advisor. “It can’t be the war in Vietnam,” she told him. “I grew up in a Jewish community full of Holocaust survivors, and you don’t see Holocaust survivors in mental hospitals. You don’t see Holocaust survivors being so disabled.”

His response: “Rachel, that is a testable hypothesis.”

At the beginning of her research, Yehuda came across a Holocaust survivor who had many symptoms common with PTSD. “I couldn’t help but ask her: how did you live with your symptoms for so long? Why didn’t you ever seek treatment?,” she said. According to Yehuda, only three per cent the people she studied had ever been to a mental health professional in their lives. “Her response to me was: where am I supposed to go?”

It was then that Yehuda decided to open the first clinic for Holocaust survivors at Mount Sinai with a program dedicated to their treatment. She has spent more than 30 years conducting extensive research and interviewing Holocaust survivors and their children.

“What blew me away even more was the Holocaust survivors with PTSD also had lower cortisol levels,” she said.

During this first part of her research, Yehuda found that changes in DNA function, gene expression, brain structure and function, neurochemistry, metabolism, hormone regulation and immune function are all possible effects of trauma. “All these things can persist well beyond the effects of the fight-or-flight response,” she said.

Further on in her studies, Yehuda came across literature that disputed the myth of traumatic damage to the second generation. “Interestingly, that literature came from Montreal. A lot of that literature was written by second-generation Holocaust survivors,” she said. This inspired Yehuda to ask more questions and develop hypotheses. “Do Holocaust offspring have more mental health problems? Do they show biologic alterations that reflect psychiatric vulnerability? If so, do these biological alterations transmit somehow through the experience of being raised by Holocaust survivors?,” she said.

To test her hypotheses, Yehuda decided to ask the Holocaust survivors she had initially studied if she could interview their children. What she learned from this research was that the higher levels of mental illness and low levels of cortisol in these children were caused by a biological change in their parent which occurred in response to surviving the Holocaust.

According to Yehuda, parental trauma can affect the next generation in many different ways including in utero and postnatally. Another conclusion drawn from her epigenetics study was that, when exposed to something traumatic during pregnancy, as many as three generations can be affected.

“The mother is affected, her fetus is affected and the fetuses gametes are affected. That is one way in which this exposure [to trauma] and pregnancy might have effects,” she said.

Through her research, the conclusion that trauma can be transmitted intergenerationally led Yehuda to form a new hypothesis: what gets transmitted to the offspring of trauma survivors isn’t the trauma itself, but rather the body’s solution for dealing with trauma. “I can’t prove this yet, but I think it is true,” Yehuda said. “Maybe someone in this room will prove it, because you are young and science is a great field, and we now have the tools and techniques to be able to do so.”